Self-etching dental materials based on (meth)acrylamide phosphates

ABSTRACT

Polymerizable dental material, characterized in that it contains at least one (meth)acrylamide phosphate of the following general formula (I): 
     
       
         
         
             
             
         
       
     
     in which R 1  is H or CH 3 ; R 2  is H or a C 1 -C 4  alkyl radical or forms together with the nitrogen atom to which it is bonded and one or more atoms which belong to R 3  or R 3′  a heterocyclic ring; R 3 , R 3′  independently of each other are a linear or branched aliphatic C 1 -C 50  radical with a valency of m+n or p+n, an aromatic C 6 -C 18  radical with a valency of m+n or p+n, or a cycloaliphatic, araliphatic or heterocyclic C 3 -C 18  radical with a valency of m+n or p+n, wherein the carbon chains of the radical or radicals can be interrupted by O, S, CONR 4 , OCONH, or form together with one or more atoms which belong to R 2  and the nitrogen atom, to which the R 2  is bonded a heterocyclic ring, R 3′  being H if p=0, and R 4  being H, C 1 -C 10  alkyl, C 6 -C 12  aryl, C 6 -C 10  aralkyl or a bicyclic C 4 -C 12  radical; n is 1, 2, 3 or 4 if p=0, and is 1 or 2 if p≠0; m is 1, 2, 3 or 4; p is 0, 1, 2, 3 or 4; x is 0 or S.

This application is a continuation of U.S. patent application Ser. No.11/211,938, filed Aug. 25, 2005, which claims priority to German PatentApplication Serial No. 10 2004 061 925.5, filed Dec. 22, 2004, which arehereby incorporated by reference in their entirety.

The present invention relates to (meth)acrylamide phosphates with a highhydrolysis resistance which are suitable in particular as adhesioncomponent for self-etching dental materials such as adhesives, coatingmaterials and composites.

Nowadays self-etching, self-conditioning dentine-enamel adhesives areincreasingly used in restorative dentistry. These adhesives are mostlyconstructed such that they contain an adhesion monomer with acidfunction, one or more non-acid comonomers, solvent, a polymerizationinitiator and optionally further additives. Suitable as polymerizableadhesion monomers are above all acid monomers which on the one handexhibit a high reactivity during radical polymerization and on the otherhand are capable of conditioning the hard tooth substance sufficientlyrapidly. Known examples of such acid monomers are carboxylic acidmethacrylates, such as 4-MET (4-methacryloyloxyethyloxycarbonyl phthalicacid), MAC-10 (10-methacryloyloxydecyl malonic acid) or acidmethacrylate phosphates, such as MDP (10-methacryloyloxydecyl dihydrogenphosphate) or MEP (2-methacryloyloxyethyl dihydrogen phosphate):

In this connection acid dimethacrylates are also known which, like PMDM(addition product of 1 mol of pyromellitic acid anhydride with 2 mol of2-hydroxyethyl methacrylate) or GDMP[(1,3-dimethacryloyloxy)-prop-2-yl-dihydrogen phosphate], arecharacterized, because of their cross-linking properties, by a highpolymerization activity:

Water is used in most cases as solvent or co-solvent in enamel-dentineadhesives, as it promotes the wetting of the hard tooth substance. Theester bonds of the methacrylates are however known to be hydrolyzedunder acid, aqueous conditions. Through the hydrolysis of the monomers,the corresponding adhesive loses its function, and the adhesion effectclearly decreases over time. Therefore the acid monomers are storedwater-free and mostly separate from the other adhesive constituents.They are either mixed shortly before use with the aqueous part orapplied separately to the tooth surface. It would be of great advantageif hydrolysis-stable adhesives could be prepared which combine all thecomponents in one composition.

Hydrolysis-stable acryl phosphonic acids are known from EP 0 909 761 A1and DE 102 34 326 in which polymerizable (meth)acryl groups are bondedto the radical of the molecule via ether-, thioether-, or viacarbon-carbon bonds.

EP 1 169 996 A1 discloses dental materials based on (meth)acrylamidephosphonic acids which, because of a relatively long-chain bridgebetween phosphonic acid group and reactive double bond, are said to havea high hydrolysis stability and improved adhesion properties.

WO 03/035013 and WO 03/013444 disclose self-etching, self-conditioningdental adhesives based on (meth)acrylamides containing acid groups, withmonomers containing sulfonic acid and phosphonic acid groups beingpreferred. These compounds can be obtained synthetically only withdifficulty.

Curable compositions are known from DE 0 333 503 A2 which contain fillerwhich has been treated with polymerizable organic phosphoric- orphosphonic acid compounds. The compositions can additionally containacid monomers.

The object of the invention is to provide a dental material which can becured by means of radical polymerization, at the same time showing ahigh polymerization tendency, which is insensitive to hydrolysis in thepresence of water at room temperature and is thus storage-stable andcapable of etching the hard tooth substance.

The object is achieved according to the invention by polymerizabledental materials which contain at least one (meth)acrylamide phosphateof the following general formula (I) or a pyrophosphate thereof:

in which

-   R¹ is H or CH₃;-   R² is H or a C₁-C₄ alkyl radical or forms together with the nitrogen    atom to which it is bonded and one or more atoms which belong to R³    or R^(3′) a heterocyclic ring;-   R³, R^(3′) independently of each other are a linear or branched    aliphatic C₁-C₅₀ radical with a valency of m+n or p+n, an aromatic    C₆-C₁₈ radical with a valency of m+n or p+n, or a cycloaliphatic,    araliphatic or heterocyclic C₃-C₁₈ radical with a valency of m+n or    p+n, wherein the carbon chains of the radical or radicals can be    interrupted by O, S, CONR⁴, OCONH, or form together with one or more    atoms which belong to R² and the nitrogen atom to which R² is bonded    a heterocyclic ring, R^(3′) being H if p=0, and wherein-   R⁴ is H, C₁-C₁₀ alkyl, C₆-C₁₂ aryl, C₆-C₁₀ aralkyl or a bicyclic    C₄-C₁₂ radical;-   n is 1, 2, 3 or 4 if p=00, and    -   is 1 or 2 if p≠0;-   m is 1, 2, 3 or 4;-   p is 0, 1, 2, 3 or 4;-   x is 0 or S.-   R² is preferably different from H.

By araliphatic or aralkyl radicals is meant groups which contain botharomatic and aliphatic radicals. A typical example of an araliphaticradical is the benzylene radical -Ph-CH₂— which comprises an aromaticphenylene group and an aliphatic methylene radical.

By carbon chain which is interrupted by other groups and/or atoms is tobe understood that these other groups or atoms are inserted into thecarbon chain, i.e. are bonded by carbon atoms on both sides. Thesegroups or atoms cannot therefore assume a terminal position. If severalgroups or atoms are integrated into a carbon chain, they must in eachcase be separated from one another by at least one carbon atom. “Carbonchain” does not mean cyclic molecule groups. The total number of groupsand/or atoms which are integrated into the carbon chain is smaller by atleast the value 1 than the number of carbon atoms in the chain.

The variables of the above formula (I) can have the following preferredmeanings independently of one another:

-   R¹=H and/or CH₃, wherein in the case m>1 the R¹ radicals can have    different meanings;-   R²=H or a C₁-C₂₀ alkyl radical or R² forms together with the    nitrogen atom to which it is bonded and one or more atoms which    belong to R³ or R^(3′) a heterocyclic ring, preferably a ring with    one nitrogen atom and 4 to 7 carbon atoms, in particular a    piperidinyl ring;-   R³, R^(3′)=independently of each other a linear or branched    aliphatic C₁-C₁₀ radical with a valency of m+n or n+p, an aromatic    C₆-C₁₀ radical with a valency of m+n or n+p, or a cycloaliphatic    C₅-C₈ radical or a araliphatic C₆-C₁₂ radical with a valency of m+n    or n+p, wherein the carbon chains of the radical or radicals can be    interrupted by 0, or R³ and/or R^(3′) form together with one or more    atoms which belong to R² and the nitrogen atom to which R² is bonded    a heterocyclic ring, preferably a ring with one nitrogen atom and 4    to 7 carbon atoms, in particular a piperidinyl ring, R^(3′) being H    if p=0;-   R⁴=H, C₁-C₆ alkyl, C₆ aryl;-   n=1 or 2 if p=0, and    -   =1 if p 0;-   m=1 or 2;-   p=0, 1 or 2;-   x=O.

Quite particularly preferred meanings of the variables of the aboveformula (I) are:

-   R¹=H or CH₃;-   R²=H or a C₁-C₃ alkyl radical or R² forms together with the nitrogen    atom to which it is bonded and one or more atoms which belong to R³    a piperidinyl ring;-   R³=a linear or branched aliphatic C₁-C₃ radical with a valency of    m+n, or R³ forms together with one or more atoms which belong to R²    and the nitrogen atom to which R² is bonded a piperidinyl ring,    quite particularly preferably a C₃ alkylene radical;-   R^(3′)=H;-   R⁴=H, C₁-C₃ alkyl;-   n=1;-   m=1 or 2;-   p=0;-   x=O.

Compounds of formula (I), in which several and in particular allvariables have one of the preferred and in particular of theparticularly preferred meanings are particularly suitable according tothe invention.

The (meth)acrylamide phosphates according to the invention of generalformula (I) (p=0; R^(3′)=H; n=1) can for example be prepared in 3 stagesstarting from reactive (meth)acrylic acid derivatives (chloride,anhydride, ester, acid) and aminoalkanols. Reactive (meth)acrylic acidderivatives and monoaminoalkanols are commercially available.Polyaminoalcohols (m>1, R²=alkyl, aryl etc.) are obtained e.g. byreaction of polyhalogen alcohols with a large excess of an aliphatic oraromatic amine (B. J. Gaj and D. R. Moore, Tetrahedron Lett. 23 (1967)2155).

Specific example:

Moreover, diaminoalcohols (m=2, n=1, R²=alkyl, aryl etc.) can beobtained by reaction of aliphatic or aromatic amines withepichlorohydrin (B. J. Gaj and D. R. Moore, Tetrahedron Lett. 23 (1967)2155).

Specific example:

A possibility for the preparation of polyaminopolyols (m,n>1) is thereaction of polyamines with epoxides.

Specific example:

In the 1st reaction stage a reactive (meth)acrylic acid derivative(R¹═H, CH₃; R′=Hal, O—CO—CR¹═CH₂, Oalkyl, OH) is reacted withaminoalkanols using the methods known from organic chemistry for thelinking of amide bonds (cf. Methoden der Organischen Chemie, HOUBEN-WEYLVolume E5 1985, Georg Thieme Verlag pages 941 ff.) to produce(meth)acrylamidoalcohols.

For this purpose in the case m=n=1 the reactive (meth)acrylic acidderivative is reacted with primary (R²═H) or secondary (R²=alkyl, aryl)monoaminoalkanols, in the case m>1, n=1 with primary (R²═H) or secondary(R²=alkyl, aryl) polyaminoalkanols, in the case m=1, n>1 with primary(R²═H) or secondary (R²=alkyl, aryl)aminopolyols and in the case m>1,n>1 with primary (R²═H) or secondary (R²=alkyl, aryl) polyaminopolyols.

The corresponding acid chlorides are preferably used in the presence ofequimolar quantities of base.

Specific example:

In the 2nd stage the (meth)acrylamidoalcohols are reacted with nequivalents of a phosphoryl compound, preferably dimethylchlorophosphate (R⁵═CH₃) (Y. Xu., G. D. Prestwich, J. Org. Chem. 67(2002) 7158).

Specific example:

In the 3rd stage the selective hydrolysis of the alkoxy groups OR⁵ takesplace, a dimethyl phosphate (R⁵═CH₃) preferably being used in which thesplitting-off is carried out with bromotrimethylsilane (Y. Xu., G. D.Prestwich, J. Org. Chem. 67 (2002) 7158).

Specific example:

Preferred examples of the (meth)acrylamide phosphates according to theinvention of the formula (I) are:

The (meth)acrylamide phosphates according to the invention of formula(I) are strongly acid and very well soluble in water or mixtures ofwater with polar solvents, such as acetone, ethanol, acetonitrile ortetrahydrofuran (THF). They are capable of etching enamel and dentinecomparably with phosphoric acid.

The (meth)acrylamide phosphates of formula (I) are hydrolysis-stableunder aqueously acid conditions at room temperature over a long period.In the context of the present invention compounds are described ashydrolysis-stable which are stable in water or in mixtures of water andwater-miscible solvents at a concentration of approximately 20 wt.-% anda pH value of approximately 2.0 at 37° C. for at least 6 weeks, i.e.hydrolyze less than 10%, preferably less than 5%.

Because of the high hydrolysis stability of the (meth)acrylamidephosphates according to the invention, mixtures with water and otherhydrolysis-stable components can be prepared therefrom which arestorage-stable at room temperature. These mixtures show, depending onthe structure and concentration of the (meth)acrylamide phosphates offormula (I), a pH value which lies between approximately 0.5 and 3.0 andare therefore capable of etching the surface of the hard tooth substance(enamel and dentine). These mixtures are therefore suitable inparticular as adhesives or cements for the dental field, quiteparticularly as self-etching enamel-dentine adhesives. (Meth)acrylamidephosphates which contain three (m+p=3) and quite particularly preferablytwo polymerizable (meth)acrylamide groups (m+p=2) are particularlyadvantageous.

The dental materials according to the invention preferably also containin addition to the (meth)acrylamide phosphates of formula (I) a solvent,particularly preferably water or a mixture of water and a water-misciblesolvent. Preferred water-miscible solvents are polar solvents such asacetone, ethanol, acetonitrile, tetrahydrofuran (THF) and mixturesthereof.

Moreover, the dental materials according to the invention can alsocontain one or more non-acid, radically polymerizable monomers, such asmono- or preferably multi-functional (meth)acryl compounds. Bymono-functional (meth)acryl compounds is meant compounds with one, bymulti-functional (meth)acryl compounds, compounds with two or more,preferably 2 to 3 (meth)acryl groups.

Preferred monofunctional (meth)acryl compounds are hydrolysis-stablemono(meth)acrylates, e.g. mesityl(meth)acrylate, or2-(alkoxymethyl)acrylic acids, e.g. 2-(ethoxymethyl)acrylic acid,2-(hydroxymethyl)acrylic acid, N-mono or N-disubstituted acrylamides,such as e.g. N-ethylacrylamide, N,N-dimethylacrylamide,N-(2-hydroxyethyl)acrylamide or N-methyl-N-(2-hydroxyethyl)acrylamide,N-monosubstituted methacrylamides, such as e.g. N-ethylmethacrylamide orN-(2-hydroxyethyl)methacrylamide, and also N-vinylpyrrolidone or allylethers and mixtures of these substances. The above-named monomers areliquid at room temperature or low-melting, i.e. they have a meltingpoint of less than 60° C., and can therefore be used as diluents.

Preferred multi-functional (meth)acrylates are e.g. hydrolysis-stableurethanes from 2-(hydroxymethyl)acrylic acid and diisocyanates, such as2,2,4-trimethylhexamethylene diisocyanate or isophorone diisocyanate,cross-linking pyrrolidones, such as e.g.1,6-bis(3-vinyl-2-pyrrolidonyl)-hexane, or bisacrylamides, such asmethylene or ethylene bisacrylamide, or bis(meth)acrylamides, such ase.g. N,N′-diethyl-1,3-bis(acrylamido)-propane,1,3-bis(methacrylamido)-propane, 1,4-bis(acrylamido)-butane or1,4-bis(acryloyl)-piperazine, which can be synthesized by reaction fromthe corresponding diamines with (meth)acrylic acid chloride. Theremaining compounds are mostly commercially available. Multi-functional(meth)acrylates act as cross-linkers during polymerization because ofthe number of polymerizable groups. Mixtures of these substances andmixtures with monofunctional (meth)acrylates are also suitable.

In order to initiate the radical polymerization the dental materialspreferably contain an initiator, particularly preferably aphotoinitiator.

Benzophenone, benzoin and their derivatives or α-diketones or theirderivatives such as 9,10-phenanthrenequinone, 1-phenyl-propan-1,2-dione,diacetyl or 4,4-dichlorobenzil are preferably used as photoinitiators.Camphorquinone and 2,2-methoxy-2-phenyl-acetophenone and in particularα-diketones are particularly preferably used in combination with aminesas reductants, such as e.g. 4-(dimethylamino)-benzoic acid esters,N,N-dimethylaminoethylmethacrylate, N,N-dimethyl-sym.-xylidine ortriethanolamine.

Redox-initiator combinations, such as e.g. combinations ofbenzoylperoxide with N,N-dimethylsym.-xylidine orN,N-dimethyl-p-toluidine are used as initiators for a polymerizationcarried out at room temperature. In addition, redox systems consistingof peroxides and reductants such as e.g. ascorbic acid, barbiturates orsulfinic acids are also particularly suitable.

Moreover, the dental materials according to the invention can be filledwith organic or inorganic particles in order to improve the mechanicalproperties or adjust the viscosity. Preferred inorganic particulatefillers are amorphous spherical oxide-based materials, such as ZrO₂ andTiO₂ as well as mixed oxides of SiO₂, ZrO₂ and/or TiO₂, nanoparticulateor microfine fillers, such as pyrogenic silicic acid or precipitationsilicic acid as well as minifillers, such as quartz, glass ceramic orglass powder with an average particle size of 0.01 to 1 μm andX-ray-opaque fillers, such as ytterbium trifluoride or nanoparticulatetantalum(V)-oxide or barium sulfate.

Dental materials for use as enamel-dentine adhesives preferably containas fillers nanoparticulate (primary particle diameters from 1 to 100 nm)amorphous spherical materials based on oxides, such as ZrO₂ and TiO₂ ormixed oxides of SiO₂, pyrogenic silicic acid or precipitated silica,ZrO₂ and/or TiO₂ and also X-ray-opaque nanoparticulate fillers, such asytterbium trifluoride, tantalum(V)-oxide or barium sulfate.

In order to obtain the self-conditioning effect of the (meth)acrylamidephosphates of Formula (I) used according to the invention, it isessential that the (meth)acrylamide phosphates are not applied to thefiller, as the phosphoric acid groups are bonded by the filler surfacein the process.

In addition, the compounds according to the invention can containfurther additives, such as e.g. stabilizers, flavours, microbiocidalagents, fluoride ion-releasing additives, optical whitening agents,plasticizers or UV absorbers.

The (meth)acrylamide phosphates of Formula (I) are particularly suitablefor the preparation of dental materials, in particular adhesives,coating materials and composites for dental purposes.

The (meth)acrylamide phosphates of Formula (I) are quite particularlysuitable for the preparation of dental adhesives and self-adhesivefixing cements, in particular for the preparation of enamel-dentineadhesives. Such adhesives and cements are characterized by a very goodadhesion to the hard tooth substance and are hydrolysis-stable undermoist conditions.

According to the invention, dental materials which contain the followingcomponents are particularly preferred:

-   a) 0.5 to 95 wt.-%, preferably 10 to 60 wt.-% and particularly    preferably 15 to 50 wt.-% (meth)acrylamide phosphate according to    Formula (I),-   b) 0.01 to 15 wt.-%, particularly preferably 0.1 to 8.0 wt.-%    initiator for the radical polymerization,-   c) 0 to 80 wt.-%, preferably 0 to 60 wt.-% and particularly    preferably 10 to 50 wt.-% non-acid monomer,-   d) 0 to 95 wt.-%, preferably 0 to 80 wt.-% and particularly    preferably 20 to 60 wt.-% solvent,-   e) 0 to 20 wt.-% filler.

The quantity of filler depends particularly on the desired applicationof the dental material. For the application as adhesive, 0 to 20 wt.-%,and for the application as cement 20 to 75 wt.-%, filler is preferred.

Other additives and adjuvants are optionally used in a quantity of 0.01to 10 wt.-%.

Unless otherwise indicated all percentages relate to the total mass ofthe material.

The invention is explained in more detail below with reference toexamples.

EXAMPLES Example 1 Phosphoric acidmono-(1-acryloyl-piperidin-4-yl)-ester (APP)

1st Stage: 1-(4-hydroxy-piperidin-1-yl)-propenone

10.11 g (0.10 mol) of 4-hydroxypiperidine was dissolved in 60 ml of 2MNaOH. The solution was stirred at room temperature for 10 minutes andthen cooled to 0° C. A solution of 9.96 g (0.11 mol) of acrylic acidchloride and 20 mg of 2,6-di-tert.-butyl-4-methylphenol (BHT) in 60 mlof chloroform was added dropwise within 2 hours at 0° C. After theaddition was completed, the clear, yellow reaction mixture was stirredat 0° C. for 1 hour, then the ice bath was removed and the mixturestirred at room temperature for another 3 hours. Organic and aqueousphases were separated. The aqueous phase was saturated with NaCl andextracted with 5×100 ml of chloroform. The combined organic phases weredried over Na₂SO₄, filtered, concentrated in a rotary evaporator afteraddition of 20 mg of BHT and dried in a fine vacuum. The yellowish oilwas taken up in 5 ml of ethyl acetate and purified by means of columnchromatography (silica gel 60, 0.035-0.070 mm, ethyl acetate). Thesolvent was concentrated in a rotary evaporator after addition of 25 mgof BHT and dried in a fine vacuum. 4.35 g (28.0 mmol, 28%) of ayellowish oil was obtained which set to form a yellowish solid whenstored in a refrigerator.

¹H NMR (CDCl₃, 400 MHz): δ=1.47-1.63 (m; 2H; CH ₂), 1-82-1.96 (m; 2H; CH₂), 3.22-3.88 (m; 2H; CH ₂), 3.77-3.88 (m; 1; CH), 3.88-3.98 (m; 2H; CH₂), 3.98-4.16 (m; 1; OH), 5.68-5.70 (dd, J=1.7 Hz, 10.8 Hz; 1H; ═CH),6.20-6.24 (dd, J=2.0 Hz, 16.6 Hz; 1H; ═CH), 6.56-6.63 (dd, J=10.6 Hz,16.8 Hz; 1H; ═CH).

¹³C NMR (CDCl₃, 100 MHz): δ=33.7 (CH₂), 34.5 (CH₂), 39.5 (CH₂), 43.2(CH₂), 66.5 (CH), 127.7 (CH₂), 127.8 (CH), 165.5 (C).

2nd Stage: Phosphoric acid(1-acryloyl-piperidin-4-yl)ester-dimethylester

2.60 g (18.0 mmol) of dimethyl chlorophosphate, 2.33 g (15.0 mmol) of1-(4-hydroxy-piperidin-1-yl)-propenone, 10 mg of hydroquinone monomethylether (MEHQ) and 10 mg of BHT were dissolved under argon in 50 ml ofdichloromethane and cooled to −5° C. in an ice bath. 2.36 g (21.0 mmol)of potassium-tert.-butylate was added accompanied by stirring. Stirringwas carried out for 30 minutes accompanied by cooling in ice, thesolution turning a brownish colour, then the ice bath was removed andthe mixture stirred at room temperature for 4 hours. 50 ml of asaturated aqueous NH₄Cl solution was then added. The mixture was stirredfor 10 minutes, then the phases were separated. The aqueous phase wasextracted with 2×50 ml of dichloromethane. The combined organic phaseswere dried over Na₂SO₄, filtered, concentrated in a rotary evaporatorafter addition of 20 mg of BHT and dried in a fine vacuum. The brown oilwas taken up in 5 ml of dichloromethane and purified by means of columnchromatography (silica gel 60, 0.035-0.070 mm, methylenechloride/ethanol 98:2). The eluent was concentrated in a rotaryevaporator after addition of 20 mg of BHT and dried in a fine vacuum.3.02 g (11.5 mmol, 76%) of a red-brown oil was obtained.

C₁₀H₁₈NO₅P Calc. C 45.63 H 6.89 N 5.32 (263.23) Found 43.12 7.19 4.96

IR: 3475 (w), 2956 (w, C—H), 1642 (s, C═O), 1608 (s, C═C), 1441 (s,C—H), 1366 (w), 1258 (s, P═O), 1219 (m), 1188 (m), 1000 (vs), 893 (m),847 (s), 791 (m), 766 (m).

¹H NMR (CDCl₃, 400 MHz): δ=1.73-1.87 (m; 2H; CH ₂), 1-92-2.03 (m; 2H; CH₂), 3.40-3.64 (m; 2H; CH ₂), 3.78 (d, J=11.1 Hz; 6H; O—CH₃), 3.81-3.94(m; 2H; CH ₂), 4.59-4.70 (m; 1; CH), 5.59 (dd, J=2.0 Hz, 10.6 Hz; 1H;═CH), 6.25 (dd, J=2.0 Hz, 16.6 Hz; 1H; ═CH), 6.61 (dd, J=10.6 Hz, 16.9Hz; 1H; ═CH).

¹³C NMR (CDCl₃, 100 MHz): δ=31.8, 32.8 (CH₂), 38.6 (CH₂), 42.4 (CH₂),54.3, 54.3 (CH₂), 73.7, 73.7 (CH), 127.6 (CH), 127.8 (CH₂), 165.4 (C).

³¹P NMR (CDCl₃, 162 MHz): δ=1.4.

3rd Stage: Phosphoric acid mono-(1-acryloyl-piperidin-4-yl)ester

1.32 g (5.0 mmol) of phosphoric aciddimethyl-[4-(N-acryloyl-piperidyl]ester and 10 mg of BHT were dissolvedunder argon in 5 ml of dichloromethane. 1.68 g (11.0 mmol) ofbromotrimethylsilane was added dropwise. The clear yellowish solutionwas stirred for 4 hours at room temperature after the addition wascompleted. For the removal of volatile components, the solution wasevacuated at 45° C. for 45 minutes. The oily yellow residue was mixedwith 5 ml of methanol. The clear yellowish solution was stirred for 18hours at room temperature and then concentrated in a rotary evaporatorand dried in a fine vacuum. The highly viscous yellowish oil was mixedwith 10 ml of dichloromethane and stirred at room temperature. A lightyellowish solid formed. This was filtered off and dried in a vacuumdrying cabinet. The process was repeated with 10 ml each of ethylacetate and acetone. The white solid was mixed with 5 ml of i-propanoland stirred at room temperature for 18 hours. The suspension wasfiltered, and the filtrate was concentrated in a rotary evaporator anddried in a fine vacuum. 0.31 g (1.3 mmol; 26%) of a white solid wasobtained.

¹H NMR (DMSO-d₆, 400 MHz): δ=1.46-1.64 (m; 2H; CH ₂), 1.77-1.95 (m; 2H;CH ₂), 3.24-3.47 (m; 2H; CH ₂), 3.69-3.87 (m; 2H; N—CH ₂), 4.31-4.43 (m;1H; O—CH), 5.66 (dd, J=2.5 Hz, 10.5 Hz; 1H; ═CH), 6.09 (dd, J=2.5 Hz,16.7 Hz; 1H; ═CH), 6.80 (dd, J=10.6 Hz, 16.7 Hz; 1H; ═CH).

³¹P NMR (DMSO-d₆, 162 MHz): δ=−0.6.

Example 2 1,3-bis-(N-acryloyl-N-propyl-amino)-propan-2-yl-dihydrogenphosphate (BAPAPP)

1st Stage: 1,3-bis-(N-acryloyl-N-propyl-amino)-2-hydroxypropane

17.43 g (0.100 mol) of 1,3-bis-(propylamino-propan-2-ol was mixed with110 ml (0.220 mol) of 2N caustic soda solution and stirred at roomtemperature for 10 minutes. The mixture was cooled to 0° C. A solutionof 19.46 g (0.215 mol) of acrylic acid chloride and 20 mg of BHT in 120ml of chloroform was added dropwise at 0° C. within 3 hours 30 minutes.After the addition was completed the reaction mixture was stirred at 0°C. for 2 hours 30 minutes. Organic and aqueous phases were separated.The aqueous phase was saturated with NaCl and extracted with 5×80 ml ofmethylene chloride. The combined organic phases were dried over Na₂SO₄,filtered, concentrated in a rotary evaporator after addition of 20 mg ofBHT and dried in a fine vacuum. The raw product was purified by means oftwo-fold column chromatography (silica gel 60, 0.035-0.070 mm, ethylacetate). 11.92 g (42.2 mmol; 42%) of the pure product was obtained as ayellowish oil.

C₁₅H₂₆N₂O₃ Calc. C 63.80 H 9.28 N 9.92 (282.39) Found 63.54 9.16 9.67

IR: 3349 (m, —OH), 2963 (m), 2933 (m), 2875 (m, C—H), 1641 (vs, C═O),1603 (vs, C═C), 1427 (vs, C—H), 1370 (m, —O—H), 1271 (w), 1229 (s), 1132(m, —C—OH), 1059 (m), 977 (s), 957 (m), 895 (w), 794 (s), 745 (m).

¹H NMR (CDCl₃, 400 MHz): δ=0.86-0.93 (m; 6H; CH ₃), 1.57-1.68 (m; 4H; CH₂—CH ₃), 3.25-3.53 (m; 8H; CH ₂—N), 4.06-4.09 (m; 1H; CH), 4.96-4.99 (m;1H; OH), 5.62-5.74 (m; 2H; ═CH), 6.25-6.38 (m; 2H; ═CH), 6.54-7.00 (m;2H; ═CH).

¹³C NMR (CDCl₃, 100 MHz): δ=11.1 (CH₃), 11.4 (CH₃), 20.6 (CH₂), 22.5(CH₂), 22.6 (CH₂), 48.8 (CH₂), 51.4 (CH₂), 51.6 (CH₂), 51.9 (CH₂), 52.0(CH₂), 70.0 (CH), 71.7 (CH), 127.2 (CH), 127.3 (CH), 127.6 (CH₂), 128.4(CH), 128.5 (CH₂), 128.7 (CH₂), 167.8 (C).

2nd Stage: 1,3-bis-(N-acryloyl-N-propyl-amino)-propan-2-yldimethylphosphate

2.60 g (18.0 mmol) of dimethylchlorophosphate, 4.24 g (15.0 mmol) of1,3-bis-(N-acryloyl-N-propyl-amino)-2-hydroxypropane, 20 mg of MEHQ and20 mg of BHT were dissolved under argon in 80 ml of dichloromethane andcooled to −5° C. in an ice bath. 2.36 g (21.0 mmol) ofpotassium-tert.-butylate was added accompanied by stirring. The mixturewas ice-cooled and stirred for 30 minutes, the solution turning aslightly yellowish colour, then the ice bath was removed, and themixture was stirred at room temperature for 4 hours. Then 80 ml ofsaturated aqueous NH₄Cl solution was added. The mixture was stirred for10 minutes, then the phases were separated. The aqueous phase wasextracted with 2×80 ml of dichloromethane. The combined organic phaseswere dried over Na₂SO₄, filtered, concentrated in a rotary evaporatorafter addition of 30 mg BHT and dried in a fine vacuum. The raw productwas purified by means of column chromatography (silica gel 60,0.035-0.070 mm), ethyl acetate/acetone 90:10→80:20). 2.74 g (11.6 mmol;50%) of a yellowish oil was obtained.

3rd Stage: 1,3-bis-(N-acryloyl-N-propyl-amino)-propan-2-yl dihydrogenphosphate

1.17 g (3.0 mmol) of 1,3-bis-(N-acryloyl-N-propyl-amino)-propan-2-yldimethylphosphate and 10 mg of BHT were dissolved under argon in 5 ml ofdichloromethane. 1.01 g (6.6 mmol) of bromotrimethylsilane was addeddropwise. The clear yellowish solution was stirred at room temperaturefor 3 hours after the addition was completed. In order to removevolatile components the solution was evacuated for 45 minutes at 45° C.The oily yellow residue was mixed with 5 ml of methanol, and the clearyellowish solution was stirred at room temperature for 18 hours. Thesolution was concentrated in a rotary evaporator and dried in a finevacuum. 1.21 g (3.3 mmol; 111%) of a slightly yellowish foam wasobtained.

Example 3 Examination of the hydrolysis stability of the phosphoric acidmono-(1-acryloyl-piperidin-4-yl) ester

A 20% solution of the phosphoric acid mono-(1-acryloyl-piperidin-4-yl)ester from Example 1 stabilized with 200 ppm of2,6-di-t-butyl-4-methylphenol in D₂O/EtOH-d₆ (1:1) was prepared, thiswas stored at 37° C. and examined by ¹H-NMR spectroscopy. After astorage time of 3 months no changes in the ¹H-NMR spectrum were found.

Example 4 Preparation of a Light-Curing Adhesive Based on(Meth)Acrylamide phosphates (MAP)

In order to examine dentine adhesion to bovine teeth dentine, adhesiveswith the following composition were prepared (values in wt.-%).

Adhesion MAP Comonomers H₂O Initiator values [wt.-%] [wt.-%] [wt.-%][wt.-%] [MPa] 14.6 BAPAPP¹⁾ A²⁾: 9.7; B³⁾: 2.1; 25.0% 1.0% 10.7 ± 2.6C⁴⁾: 47.6 14.3 APP⁵⁾ C: 45.1; D⁶⁾: 9.1; 12.8% 1.0% 11.9 ± 5.4 E⁷⁾: 5.3;F⁸⁾: 12.4 ¹⁾BAPAPP = monomer from Example 2 ²⁾A =[1-(methacryloylamino)propyl]-phosphonic acid ³⁾B =6-(N-acryloylamino)hexan-1-ol ⁴⁾C =N,N′-diethyl-1,3-propylene-bisacrylamide ⁵⁾APP = monomer from Example 1⁶⁾D = D,L-2-(acryloylamino)succinic acid ⁷⁾E =N-(5-hydroxy-pentyl)methacrylamide ⁸⁾F = Aerosil-H₂O mixture

Bovine teeth were embedded in plastic cylinders such that the dentineand the plastic were situated at one level. After grinding of thetestpieces, a layer of adhesive of the above formulation was rubbed intothe dentine surface with a microbrush for 30 seconds, gently blown withan air blower and lit with an Astralis 7 photopolymerization lamp(Ivoclar Vivadent AG) for 20 seconds. A commercially available dentalfilling composite (Tetric® Ceram, Ivoclar Vivadent AG) was then appliedto the adhesive layer and cured for 40 seconds with the Astralis 7 lamp.The testpieces were then stored in water for 24 hours at 37° C. and theadhesive shear strength measured in accordance with the ISO guideline“ISO 1994-ISO TR 11405: Dental Materials Guidance on Testing of Adhesionto Tooth Structure”.

Although preferred embodiments have been depicted and described indetail herein, it will be apparent to those skilled in the relevant artthat various modifications, additions, substitutions, and the like canbe made without departing from the spirit of the invention and these aretherefore considered to be within the scope of the invention as definedin the claims which follow.

1. Polymerizable dental material, which comprises at least one(meth)acrylamide phosphate of the following general formula (I):

in which R¹ is H or CH₃; R² is H or a C₁-C₄ alkyl radical; R³, R^(3′)independently of each other are a linear or branched aliphatic C₁-C₅₀radical with a valency of m+n or p+n, an aromatic C₆-C₁₈ radical with avalency of m+n or p+n, or a cycloaliphatic, araliphatic or heterocyclicC₃-C₁₈ radical with a valency of m+n or p+n, wherein the carbon chainsof the radical or radicals can be interrupted by O, S, CONR⁴, OCONH,R^(3′) being H if p=0, and wherein R⁴ is H, C₁-C₁₀ alkyl, C₆-C₁₂ aryl,C₆-C₁₀ aralkyl or a bicyclic C₄-C₁₂ radical; n is 1, 2, 3 or 4 if p=00,and is 1 or 2 if p≠0; m is 1, 2, 3 or 4; p is 0, 1, 2, 3 or 4; x is 0 orS.
 2. Dental material according to claim 1, in which R² is a C₁-C₄ alkylradical.
 3. Dental material according to claim 1, comprising at leastone (meth)acrylamide phosphate of formula (I′):

wherein R¹=H or CH₃; R²=H or a C₁-C₄ alkyl radical; R³=a linear orbranched aliphatic C₁-C₁₂ radical, a cycloaliphatic or a heterocyclicC₃-C₁₈, wherein the carbon chain of the radical can be interrupted by O,S, CONH, or OCONH; m=1, 2, 3 or 4; X=O or S.
 4. Dental materialaccording to claim 1, wherein at least one of the variables has one ofthe following meanings: R¹=H or CH₃; R²=H or a C₁-C₃ alkyl radical; R³=alinear or branched aliphatic C₁-C₃ radical with a valency of m+n;R^(3′)=H; R⁴=H, C₁-C₃ alkyl; n=1; m=1 or 2; p=0; x=O.
 5. Dental materialaccording to claim 1, which additionally contains a solvent.
 6. Dentalmaterial according to claim 5, which contains as solvent water or amixture of water and a solvent miscible with water.
 7. Dental materialaccording to claim 1, which additionally contains at least one non-acid,radically polymerizable monomer.
 8. Dental material according to claim7, which contains as non-acid monomer one or more monomers from thefollowing group: mono(meth)acryl compounds, mesityl(meth)acrylate,2-(alkoxymethyl)acrylic acids, 2-(ethoxymethyl)acrylic acid,2-(hydroxymethyl)acrylic acid, N-mono and N-disubstituted acrylamides,N-ethylacrylamide, N,N-dimethylacrylamide, N-(2-hydroxyethyl)acrylamide,N-methyl-N-(2-hydroxyethyl)acrylamide, N-monosubstituted methacrylamide,N-ethylmethacrylamide, N-(2-hydroxyethyl)methacrylamide,N-vinylpyrrolidone and allyl ethers.
 9. Dental material according toclaim 7, which contains as non-acid monomer one or more monomers fromthe following group: urethanes from 2-(hydroxymethyl)acrylic acid anddiisocyanates, 2,2,4-trimethylhexamethylene diisocyanate, isophoronediisocyanate, cross-linking pyrrolidones,1,6-bis(3-vinyl-2-pyrrolidonyl)-hexane, bisacrylamides, methylene andethylene bisacrylamide, bis(meth)acrylamides,N,N′-diethyl-1,3-bis(acrylamido)propane,1,3-bis(methacrylamido)-propane, 1,4-bis(acrylamido)-butane and1,4-bis(acryloyl)-piperazine.
 10. Dental material according to claim 1,which additionally contains at least one initiator for the radicalpolymerization.
 11. Dental material according to claim 1, whichadditionally contains at least one filler.
 12. Dental material accordingto claim 1, which contains the following components: a) 0.5 to 95 wt.-%(meth)acrylamide phosphate according to Formula (I), b) 0.01 to 15 wt.-%initiator, c) 0 to 80 wt.-% non-acid radically polymerizable monomer, d)0 to 95 wt.-% solvent, e) 0 to 20 wt.-% filler.
 13. Dental materialaccording to claim 12, which additionally contains f) 0.01 to 10 wt.-%of one or more further additives.
 14. Dental material comprising a) 0.5to 95 wt.-% of at least one (meth)acrylamide phosphate of the followinggeneral formula (I):

in which R¹ is H or CH₃; R² is H or a C₁-C₃ alkyl radical; R³, R^(3′)independently of each other are a linear or branched aliphatic C₁-C₅₀radical with a valency of m+n or p+n, an aromatic C₆-C₁₈ radical with avalency of m+n or p+n, or a cycloaliphatic, araliphatic or heterocyclicC₃-C₁₈ radical with a valency of m+n or p+n, wherein the carbon chainsof the radical or radicals can be interrupted by O, S, CONH, OCONH,R^(3′) being H if p=0, and wherein n is 1, 2, 3 or 4 if p=0, and is 1 or2 if p≠0; m is 1, 2, 3 or 4; p is 0, 1, 2, 3 or 4; X is O or S b) 0.01to 8 wt.-% initiator, c) 0 to 80 wt.-% non-acid radically polymerizablemonomer, d) 0 to 80 wt.-% solvent, e) 0 to 20 wt.-% filler.
 15. Dentalmaterial comprising a) 0.5 to 95 wt.-% of at least one (meth)acrylamidephosphate of the following general formula (I′):

wherein R¹=H or CH₃; R²=H or a C₁-C₄ alkyl radical; R³=a linear orbranched aliphatic C₁-C₅₀ radical, a cycloaliphatic or a heterocyclicC₃-C₁₈, wherein the carbon chain of the radical can be interrupted by O,S, CONH, or OCONH; m=1, 2, 3 or 4; X=O or S b) 0.01 to 8 wt.-%initiator, c) 0 to 80 wt.-% non-acid radically polymerizable monomer, d)0 to 80 wt.-% solvent, e) 0 to 20 wt.-% filler.
 16. Dental materialaccording to claim 14, wherein the non-acid radically polymerizablemonomer is a (meth)acrylamide monomer.
 17. Dental material according toclaim 15, wherein the non-acid radically polymerizable monomer is a(meth)acrylamide monomer.